This invention concerns a headbox for a machine for the manufacture of paper, cardboard or similar. Such a headbox is known from the British patent document 1,361,083. Its essential elements are a nozzle type, machinewide stock channel that extends into a machinewide flow-out gap. Preceding the stock channel is a turbulence generator in the form of a machinewide bundle of numerous turbulence pipes. These extend in a preferably straight direction of flow while--viewed in longitudinal section--they converge in flow direction. However, the invention is applicable also with other turbulence pipe setups, for instance where the turbulence pipes are parallel to one another.
As commonly known, the turbulence generator serves to impart to the fibrous stock suspension that flows through the headbox a microturbulent state. This is to prevent the formation of flakes in the fiber suspension which would cause a disuniform fiber distribution in the web being formed (on the following paper machine wire).
To date, care has been taken that the geometric shape of all turbulence pipes of a turbulence generator is as uniform as possible, except for at most the marginal zones. Nevertheless there is often a risk of a streaky fiber deposition on the paper machine wire and, thus, of the creation of longitudinal stripes in the finished paper web. It has heretofore not been possible to eliminate this risk with sufficiently high safety.
Therefore, the problem underlying the invention is to improve the initially described headbox so that the risks of creating longitudinal stripes in the paper web will be avoided with a still higher safety than heretofore, thereby increasing the uniformity of the fiber distribution in the finished web (i.e., improvement of the "formation").